1. Field of the Invention
The present invention relates to a die casting device, specifically to a die casting technique, in which the cavity of a die is decompressed to conduct casting.
2. Description of Related Art
In conventional die casting, the following techniques are used, namely: feeding a predetermined amount of molten metal into an injection sleeve having a feeding orifice; after the feeding, moving an injection tip by drive means at a predetermined timing; and injecting the molten metal from the injection sleeve into the cavity of a die at high pressure (For example, refer to Japanese Patent Application Publication No. 2003-245768 (JP 2003-245768 A), Japanese Patent Application Publication No. 4-258357 (JP 4-258357 A), Japanese Patent Application Publication No. 2002-239708 (JP 2002-239708 A), and Japanese Patent Application Publication No. 2004-167499 (JP 2004-167499 A)).
In the die casting device disclosed in JP 2003-245768 A, molten metal is taken out of a molten-metal holding furnace by a ladle, and it is fed into the feeding orifice of an injection sleeve by the ladle.
However, in the configuration disclosed in JP 2003-245768 A, as it is difficult to adjust the amount of ladled molten metal, it is difficult to improve the feeding accuracy. In addition, as molten metal touches the atmosphere at the time of feeding from the ladle into the sleeve, there are problems that the temperature of the molten metal decreases, and/or the product quality deteriorates due to gas such as dissolved hydrogen and an oxidized film produced in the molten metal.
On the other hand, the die casting devices disclosed in the above mentioned JP 4-258357 A and JP 2002-239708 A are configured in a manner that a feeding pipe and a feeding orifice of the injection sleeve are directly joined together, and molten metal is fed through the feeding pipe in order to avoid the molten metal from touching the atmosphere.
However, because the injection sleeve is fed with molten metal of high temperature, deformation is incurred in the injection sleeve due to the heat of the molten metal, which tends to cause vibrations at the time of injection. In the configurations disclosed in JP 4-258357 A and JP 2002-239708 A, there are problems that the feeding pipe directly joined to the injection sleeve, and/or its junction are damaged due to abrasion and/or vibration at the time of injection.
In addition, the die cast device disclosed in JP 2004-167499 A is configured in a manner that a cover is provided between a feeding pipe and a feeding orifice of the injection sleeve so as to avoid molten metal from touching the atmosphere at the time of molten-metal feeding.
However, according to the technique disclosed in JP 2004-167499 A, the feeding pipe is not directly joined to the injection sleeve, and thus a separate structure for supporting the feeding pipe is required. In addition, there is a possibility that the strength of the cover is insufficient with respect to the heat of the molten metal at the time of molten-metal feeding and/or the pressure at the time of decompressing a cavity, and that the cover is damaged.